Effect of dietary protein levels on ammonia concentration and growth of Tilapia rendalli (Boulenger, 1896), raised in concrete tanks

Tilapia rendalli juveniles (±9.5 g) were cultured in concrete tanks to determine the effect of four dietary protein levels (30, 35, 40 and 45% crude protein (CP) in feed on ammonia concentration and growth performance of the fish, stocked at 15 fish per tank. Fish were monitored for a period of 90 days. Fish that were fed on 40% CP diet had significantly (P<0.05) higher weight gain, growth, and feed conversion ratio (FCR). Ammonia concentration was significantly higher (P<0.05) in tanks where the 45% CP diet was administered, and where also poor growth and survival rate was observed. Poor growth performance of the fish at inadequate (below 30% CP) and oversupply (above 40% CP) protein diet is evidence of the importance of taking precautions on the levels of protein inclusion in diet in tank culture. Higher dietary protein diet precipitates ammonia accumulation, thus compromising growth performance. Based on findings in this study, optimal protein level of 40% CP is recommended for tank culture.   Key words: Ammonia concentration, dietary protein, growth performance, Tilapia rendalli.